Portable electronic imaging systems employing an electronic image display internal to an optical viewing assembly are well known and are generally designed for two primary applications. The most common is the camcorder, comprising a monocular viewfinder to provide a magnified virtual view of the recorded scene. Such viewfinders provide only a limited apparent field of view and a limited exit pupil and eye relief, and further limit viewing to one eye, resulting in an inconvenient configuration for the user and limited utility for other applications. One solution to this problem has been to replace the viewfinder with a larger flat television display. This solution provides comfortable viewing by both eyes with no exit pupil and eye relief restrictions. However, a large display costs and weighs significantly more than the conventional viewfinder, requires a great amount of battery power, and also provides only a limited field of view.
The second common application of optical viewing assemblies in electronic imaging systems is the head mounted display for night vision or virtual reality applications. Typically employing a biocular or binocular optical system to view one or two display panels, such systems generally provide wider fields of view and larger exit pupils than camcorder viewfinders by employing more elaborate and expensive optical systems, larger display panels, or both. However, the greater cost of such systems combined with the limited utility of head mounted displays results in restricted markets and subsequently in restricted development and production resources.
Generally the electronic image display is a relatively expensive part of a binocular electronic imaging system, particular if the imaging system incorporates separate displays for each eye. Accordingly, the cost of such systems may be reduced by utilizing a single electronic image display to display the binocular image to both eyes. Prior art compact optical systems for providing binocular viewing of a single display require an expensive and heavy beam-splitting cube necessary to preserve the orientation of the image to both eyes. Moreover, the position of a beam splitting cube between the two eye-lenses restricts the relative proximity thereof and accordingly limits the ergonomic utility of the optical system.